This invention relates to automotive electric generators or alternators. In many systems, the generator includes an alternator and a voltage regulator. Often the voltage regulator (hereinafter regulator) is integral with the alternator, but not necessarily so. The regulator controls the output voltage of the alternator to a calibrated voltage set point. The voltage is controlled by a regulation scheme, which adjusts the duty cycle on the rotor winding (often called the field or field coil) of the alternator. The output of the alternator is directly related to the duty cycle of the field coil, and the rotational speed of the rotor. The regulator also establishes a desired system voltage (called a set-point voltage) that the voltage regulator attempts to maintain. This set-point voltage may be based on temperature, a pulse width modulated (PWM) based customer input, or a serial data link customer input.
For normal operation, when the actual system voltage (for example, voltage measured at the battery) increases above the set-point voltage, the average duty cycle on the field is decreased in an attempt to decrease the alternator output voltage, and thereby the system voltage, to the set-point. When the actual system voltage decreases below the set-point voltage, the average duty cycle on the field is increased in an attempt to increase the system voltage to the set-point This formulates the basis of PWM field control and establishes a limit cycle around the set-point voltage.
Unfortunately, certain conditions and faults (e.g., the loss of the main clock, power supply or interconnection and the like) may occur within the voltage regulators that result in completely disabling the output to the field coil and thereby resulting in loss of generated power. Therefore, it would be desirable to establish a capability to maintain alternator operation and improve vehicle operability in light of such considerations.
Disclosed herein is an electric power generating system comprising: an alternator and a voltage regulator, the voltage regulator including a normal field control and a redundant field control, and a selection apparatus for selecting between the normal field control and the redundant field control.
Also disclosed herein is an electric machine comprising: an alternator, and a regulator, the regulator includes a normal field control and a redundant field control coupled to the alternator, and a selection apparatus for selecting between the normal field control and the redundant field control.
Further disclosed, is a method of providing excitation to an electric machine in an electric power generating system with an alternator and a regulator. The method comprises: receiving a field default signal indicative of an inoperative normal field control and a normal field command responsive to the normal field control, indicative of a desired duty cycle command to a field coil of an alternator in a generator including an alternator and regulator. The method further includes determining if a supply voltage is greater than a selected value and formulating a default field command; transmitting a field drive responsive to the default field command to the field coil of the alternator if the field default signal is asserted. The regulator includes a normal field control and a redundant field control.
An electric machine for providing a source of electrical power, comprising: an alternator; a first means for determining and providing an excitation for a field coil of the alternator; a second means for determining providing an excitation for the field coil of the alternator, the second means providing the excitation if the first means is inoperative; and a means for determining whether the first means is inoperative.
A regulator for providing excitation to an alternator in an electric power generating system with an alternator comprising: means for receiving a field default signal indicative of an inoperative normal field control; means for receiving a normal field command responsive to the normal field control, indicative of a desired duty cycle command to a field coil of an alternator in a generator including an alternator and regulator. The regulator further includes: means for determining if a supply voltage greater than selected value and formulating a default field command; means for transmitting a field drive responsive to the default field command to the field coil of the alternator if the field default signal is asserted. The regulator also includes an operational field control and a redundant field control.